third_party/WebKit/Source/platform/audio/AudioDelayDSPKernel.cpp

/*
 * Copyright (C) 2010, Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1.  Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

#include "platform/audio/AudioDelayDSPKernel.h"
#include "platform/audio/AudioUtilities.h"
#include "wtf/MathExtras.h"
#include <cmath>

namespace blink {

const float SmoothingTimeConstant = 0.020f;  // 20ms

AudioDelayDSPKernel::AudioDelayDSPKernel(AudioDSPKernelProcessor* processor,
                                         size_t processingSizeInFrames)
    : AudioDSPKernel(processor),
      m_writeIndex(0),
      m_firstTime(true),
      m_delayTimes(processingSizeInFrames) {}

AudioDelayDSPKernel::AudioDelayDSPKernel(double maxDelayTime, float sampleRate)
    : AudioDSPKernel(sampleRate),
      m_maxDelayTime(maxDelayTime),
      m_writeIndex(0),
      m_firstTime(true) {
  ASSERT(maxDelayTime > 0.0 && !std::isnan(maxDelayTime));
  if (maxDelayTime <= 0.0 || std::isnan(maxDelayTime))
    return;

  size_t bufferLength = bufferLengthForDelay(maxDelayTime, sampleRate);
  ASSERT(bufferLength);
  if (!bufferLength)
    return;

  m_buffer.allocate(bufferLength);
  m_buffer.zero();

  m_smoothingRate = AudioUtilities::discreteTimeConstantForSampleRate(
      SmoothingTimeConstant, sampleRate);
}

size_t AudioDelayDSPKernel::bufferLengthForDelay(double maxDelayTime,
                                                 double sampleRate) const {
  // Compute the length of the buffer needed to handle a max delay of
  // |maxDelayTime|. One is added to handle the case where the actual delay
  // equals the maximum delay.
  return 1 + AudioUtilities::timeToSampleFrame(maxDelayTime, sampleRate);
}

bool AudioDelayDSPKernel::hasSampleAccurateValues() {
  return false;
}

void AudioDelayDSPKernel::calculateSampleAccurateValues(float*, size_t) {
  ASSERT_NOT_REACHED();
}

double AudioDelayDSPKernel::delayTime(float sampleRate) {
  return m_desiredDelayFrames / sampleRate;
}

void AudioDelayDSPKernel::process(const float* source,
                                  float* destination,
                                  size_t framesToProcess) {
  size_t bufferLength = m_buffer.size();
  float* buffer = m_buffer.data();

  ASSERT(bufferLength);
  if (!bufferLength)
    return;

  ASSERT(source && destination);
  if (!source || !destination)
    return;

  float sampleRate = this->sampleRate();
  double delayTime = 0;
  float* delayTimes = m_delayTimes.data();
  double maxTime = maxDelayTime();

  bool sampleAccurate = hasSampleAccurateValues();

  if (sampleAccurate) {
    calculateSampleAccurateValues(delayTimes, framesToProcess);
  } else {
    delayTime = this->delayTime(sampleRate);

    // Make sure the delay time is in a valid range.
    delayTime = clampTo(delayTime, 0.0, maxTime);

    if (m_firstTime) {
      m_currentDelayTime = delayTime;
      m_firstTime = false;
    }
  }

  for (unsigned i = 0; i < framesToProcess; ++i) {
    if (sampleAccurate) {
      delayTime = delayTimes[i];
      if (std::isnan(delayTime))
        delayTime = maxTime;
      else
        delayTime = clampTo(delayTime, 0.0, maxTime);
      m_currentDelayTime = delayTime;
    } else {
      // Approach desired delay time.
      m_currentDelayTime += (delayTime - m_currentDelayTime) * m_smoothingRate;
    }

    double desiredDelayFrames = m_currentDelayTime * sampleRate;

    double readPosition = m_writeIndex + bufferLength - desiredDelayFrames;
    if (readPosition >= bufferLength)
      readPosition -= bufferLength;

    // Linearly interpolate in-between delay times.
    int readIndex1 = static_cast<int>(readPosition);
    int readIndex2 = (readIndex1 + 1) % bufferLength;
    double interpolationFactor = readPosition - readIndex1;

    double input = static_cast<float>(*source++);
    buffer[m_writeIndex] = static_cast<float>(input);
    m_writeIndex = (m_writeIndex + 1) % bufferLength;

    double sample1 = buffer[readIndex1];
    double sample2 = buffer[readIndex2];

    double output =
        (1.0 - interpolationFactor) * sample1 + interpolationFactor * sample2;

    *destination++ = static_cast<float>(output);
  }
}

void AudioDelayDSPKernel::reset() {
  m_firstTime = true;
  m_buffer.zero();
}

double AudioDelayDSPKernel::tailTime() const {
  // Account for worst case delay.
  // Don't try to track actual delay time which can change dynamically.
  return m_maxDelayTime;
}

double AudioDelayDSPKernel::latencyTime() const {
  return 0;
}

}  // namespace blink